Project Summary With an aging population and pulmonary infections becoming an increasingly significant cause of morbidity and mortality, there is an urgent need to investigate molecular pathways underlying these impairments and devise new therapeutics that can stimulate innate immune responses within this population. Our results demonstrate aged hosts have impaired inflammasome activation, decreased gene expression of several key components of the NLRP3 signaling pathway, reduced caspase-1 activity, and diminished IL1? production in response to in vitro and in vivo infection with influenza or S. pneumoniae. Using in vitro and in vivo aging murine models of primary influenza and secondary S. pneumoniae infection, we will employ cellular and molecular techniques to test our overall hypothesis that the NLRP3 inflammasome is necessary for survival and age associated impairments in ER and mitochondrial Ca2+ homeostasis result in impaired activation of the NLRP3 inflammasome in aged lung; thereby, resulting in increased pathogenesis, tissue injury, and pneumonic edema in the elderly lung. To test this hypothesis, we will examine the role of the unfolded protein response (UPR) on inflammasome activity in response to influenza (Aim 1) and the impact of overly heightened pathogenic mediated UPR on inflammasome activation in response to secondary S. pneumoniae infection (Aim 2). Summary and impact: As pulmonary pneumococcal infections remain a substantial cause of morbidity and mortality in the elderly, even in an era of routine adult vaccination, there is a pressing need to identify mechanistic pathways that regulate innate immune responses and investigate novel therapeutics and treatment strategies that reduce serious disease and improve clinical outcomes. By establishing and dissecting a pivotal mechanistic link between UPR activation and inflammasome signaling in aged lung, this research proposal has high potential to elucidate innovative regulatory pathways and expand current understanding of age associated changes in ER homeostasis. Therapeutic strategies designed to target defects in innate signaling in the aged host will aid in circumventing emergent strains of antibiotic resistant bacteria and may be utilized for treatment against a wide variety of pathogenic stimuli. Completion of the proposed aims will further define the role of the NLRP3 inflammasome as an important innate signaling pathway during influenza and secondary S. pneumoniae infections as well as yield new therapeutics that can be readily tested in primary human cells and evaluated in additional model systems.